Image projector

ABSTRACT

An image projector includes a first deflector configured to deflect a first optical path and to form a second optical path, a second deflector configured to deflect the second optical path and to form a third optical path, a shifter configured to shift a projection lens in a vertical direction which corresponds to a longitudinal direction of the projected surface among directions orthogonal to an optical axis of the projection lens, a housing configured to house the first deflector and the second deflector, and a fixed plate fixed onto the housing at an end on an installing surface side of the housing, the projection lens and the shifter being fixed onto the fixed plate, wherein the third optical path is closer to an installing surface of the housing than the first optical path.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image projector.

2. Description of the Related Art

Japanese Patent No. 3,339,504 discloses an image projector configured todeflect an optical path of light emitted from a light source, to arrangean optical path of a projection lens above the optical path of the lightemitted from the light source, and to make vertically shiftable theprojection lens of the projection lens by the shifter.

It is difficult to miniaturize such a conventional image projector thatdeflects the optical path and includes the shifter for the projectionlens because the vertical length (or height) of the housing is likely toincrease. In addition, when the projection lens and the shifter arefixed onto a fixed plate and when a lower end of the fixed plate isfixed onto a bottom plate of a housing of the image projector, thevertical length or height of the fixed plate becomes large and the fixedplate is likely to incline in the horizontal direction. As a result,projected image quality may deteriorate as an image plane of theprojection lens fluctuates.

SUMMARY OF THE INVENTION

The present invention provides a smaller image projector having a goodcharacteristic.

An image projector according to the present invention includes an imagedisplay element configured to display an original image, a firstdeflector configured to deflect a first optical path through which lightfrom a light source can pass, and to form a second optical path, asecond deflector configured to deflect the second optical path and toform a third optical path, a projection lens configured to project lightthat has transmitted the image display element and the third opticalpath, onto a projected surface, a shifter configured to shift theprojection lens in a vertical direction which corresponds to alongitudinal direction of the projected surface among directionsorthogonal to an optical axis of the projection lens, a housingconfigured to house the image display element, the first deflector, andthe second deflector, and a fixed plate fixed onto the housing at an endon an installing surface side of the housing, the projection lens andthe shifter being fixed onto the fixed plate, wherein the third opticalpath is closer to an installing surface of the housing than the firstoptical path.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical path diagram of an image projector of thisembodiment installed on a projection stage.

FIG. 2 is an optical path diagram when the image projector illustratedin FIG. 1 is hung down from a ceiling.

FIG. 3 is an optical path diagram of an image projector of a firstembodiment corresponding to FIG. 1.

FIG. 4 is an optical path diagram of an image projector of a secondembodiment corresponding to FIG. 1.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is an optical path of an image projector (projection type displayapparatus) of this embodiment installed on a projection stage 8. In FIG.1, reference numeral 1 denotes a light source lamp. Reference numeral 2denotes a first optical path that extends in a horizontal direction inwhich light emitted from the light source lamp 1 passes. Referencenumeral 3 denotes a housing of the image projector.

Reference numeral 4 is a first deflector configured to deflect the firstoptical path 2 by 90° and to form a vertically extending second opticalpath 5. Reference numeral 6 is a second deflector configured to deflectthe second optical path 5 by 90° and to form a horizontally extendingthird optical path 7. A deflecting angle made by each of the firstdeflector 4 and the second deflector 6 is not limited to 90°.

In this embodiment, the first optical path 2 is parallel to the thirdoptical path 7, and each of the first optical path 2 and the thirdoptical path 7 is perpendicular to the second optical path 5. The secondoptical path extends in the vertical direction.

As a light deflecting method, each of the first deflector 4 and thesecond deflector 6 can use reflection using a mirror or a polarizationsplitting film. The second deflector 6 is closer to the installingsurface of the housing 3 than the first deflector 4.

In FIG. 1, an installing surface 3 a of the housing 3 is a (bottom)surface of the bottom plate of the housing 3 on the side of theprojection stage 8. In FIG. 1, the installing surface side of thehousing 3 is the lower side and the side opposite to the installingsurface side of the housing 3 is the upper side, whereas in FIG. 2,which will be descried later, the housing 3 is fixed onto a ceilingupside down and the vertical relationship is inverted.

The light flux from the light source lamp 1 passes the first opticalpath 2, is downwardly reflected by the first deflector 4, passes thesecond optical path 5, is reflected by the second deflector 6, passesthe third optical path 7, and enters the projection lens (projectionoptical system) 10.

The image projector further includes an image display element (notillustrated) configured to display an original image, and the projectionlens 10 projects image light that has passed the image display elementand the third optical path 7 onto a projected surface (screen) 12.

The projection lens 10 is configured shiftable by the shifter 11. Theshifter 11 shifts the projection lens 10 in the vertical direction (inFIG. 1) which corresponds to the longitudinal direction of the projectedsurface 12 among directions orthogonal to the optical axis of theprojection lens 10. The shifter 11 and the projection lens 10 are fixedonto the fixed plate 9. An end 9 a of the fixed plate 9 on the lowerside is fixed onto the exterior of the lower part of the housing 3(which is the installing surface 3 a of a member fixed onto theinstalling surface 3 a).

The image display element (not illustrated), the first deflector 4, andthe second deflector 6 are housed in the housing 3, but the projectionlens 10 partially projects from the housing 3. In addition, the fixedplate 9 and the shifter 11 may not be housed in the housing 3.

Conventionally, the first optical path 2 is closer to the installingsurface of the housing 3 than the third optical path 7 due to the heavylight source lamp 1 is heavy or due to another reason. However, thisembodiment arranges the third optical path 7 closer to the installingsurface of the housing 3 than the first optical path 2.

As a result, the projection lens 10 is arranged at the lower part of thehousing 3, and a distance D between the lower end 9 a of the fixed plateand the optical axis of the projection lens 10 becomes smaller than theconventional one and thereby the image projector can be made smaller inthe vertical direction (height direction). For example, as illustratedin FIG. 1, a hatched space V at the upper portion of the projection lens10 may be removed from the housing 3 and the housing 3 may be madesmaller, or a functional component may be provided to the space V forthe effective utilization of the space V.

In addition, the cost can be reduced due to the reduced vertical length(height) of the fixed plate 9.

Moreover, due to the shorter length (height) of the fixed plate 9 in thevertical direction, the fixed plate 9 becomes less likely to incline inthe horizontal direction (lateral direction in FIG. 1). Therefore, thefixed plate 9 becomes less likely to incline irrespective of the weightof the projection lens 10 and the image display element's displaysurface (not illustrated) and the image plane of the projection lens 10are less likely to fluctuate, the image display element and theillumination optical system (not illustrated) used to illuminate theimage display element are less likely to incline. Since the imagequality on the projected surface 12 can be maintained, the opticalcharacteristic of the image projector can be maintained.

In the longitudinal direction as the shifting direction of the shifter11, assume a shift amount S2 by which the projection lens 10 can beshifted in the downward direction corresponding to the installingsurface side of the housing 3 and a shift amount S1 by which theprojection lens 10 can be shifted in the upward direction correspondingto the side opposite to the installing surface side of the housing 3. Inthis case, the shift amount S1 in the upward direction may be the sameas the shift amount S2 in the downward direction (i.e., S1=S2) but theshift amount S1 may be larger than the shift amount S2. In the lattercase, the height of the housing 3 can become smaller and the fixed plate9 may be made shorter as the shift amount S2 decreases. Thereby, thecost reduction and the maintenance of the optical characteristic areobtained.

In addition, an interface substrate 13 and a main substrate 14 arefurther provided by mounting an input/output terminal 13 a between thefirst optical path 2 and the installing surface 3 a of the housing 3.This configuration can reduce the dead space in the housing, effectivelyutilize the internal space of the housing 3, and miniaturize the housing3. The input/output terminal 13 a is connectable to an interfaceconnector, and can transmit and can receive a variety of signalsincluding image information to be projected onto the projected surface12.

FIG. 2 is an optical path diagram of the image projector hung from aceiling 16. When the image projector is hung down from the ceiling 16,the housing is arranged upside down, a lifting hook 15 illustrated inFIG. 2 is attached onto the bottom surface (or installing surface) ofthe housing 3, and the lifting hook 15 is fixed onto the ceiling 16.

In this case, in addition to the above effect, the fixed plate 9 can bearranged near the lifting hook 15 that supports the housing 3 and highrigidity, and this configuration can restrain the image degradation bypreventing the fall of the projection lens 10, and improves the opticalcharacteristic of the image projector.

Moreover, since the interface substrate 13 is arranged near the liftinghook 15, cables 18 connected to the input/output terminal 13 a can betrained along the lifting hook 15 by the shortest distance. Since thecable 18 becomes shorter, the influences of noises can be reduced andthe electric characteristic of the image projector and the image qualityof the projected image can be maintained. In addition, a cover member 17configured to cover the cable 18 can be made smaller and the projectionby the cover member 17 can become easier.

The end 9 a of the fixed plate 9 is screwed onto the exterior 3 a of thehousing 3 in FIGS. 1 and 2, but they may be fixed onto the housing 3 onthe side opposite to the installing surface side of the housing 3 so asto enhance the fall preventive effect of the fixed plate 9. As a fixingmethod, one of the fixed plate 9 and the housing 3 is provided with aboss and the other is provided with a concave engageable with the boss,or a fixation using a screw may be used.

The fixed plate 9 may be connected one or more optical element, such asa prism, as described later.

A description will now be given of an example of an optical systemarranged in the first optical path 2, the second optical path 5, and thethird optical path 7.

First Embodiment

FIG. 3 is a concrete optical path diagram of an image projectoraccording to a first embodiment corresponding to FIG. 1. In FIG. 3,reference numeral denotes a light source. Reference numeral 22 denotes a(parabolic) reflector configured to reflect light from the light source21 to the right side in FIG. and to convert the light into approximatelycollimated light. The light source 21 and the reflector 22 correspond tothe light source lamp 1 in FIG. 1. The light source 21 emits, forexample, white light.

An illumination optical system is arranged in the first optical path 2and configured to uniformly Kohler-illuminate the reflectiveliquid-crystal panel 29. The illumination optical system includes afirst fly-eye lens 23 a, a second fly-eye lens 23 b, a polarizationconversion element 24, and condenser lenses 25 a, 25 b.

The first fly-eye lens 23 a includes panels and rectangular lenseshaving similar shapes in a matrix. The second fly-eye lens 23 b includeslenses corresponding to respective lenses of the first fly-eye lens 23a. The first and second fly-eye lenses 23 a, 23 b form a secondary lightsource configured to split light fluxes and to uniformly illuminate thereflective liquid-crystal panel 29. The polarization conversion element24 converts non-polarized light from the light source 21 into linearlypolarized light, such as P-polarized light, having a specificpolarization direction.

Reference numeral 26 denotes a mirror corresponding to the firstdeflector 4, reference numeral 27 denotes a polarization beam splitter(prism), and reference numeral 28 denotes a polarization splitting filmof the polarization beam splitter 27. Reference numeral 29 denotes animage display element configured to form an original image that includesa reflective liquid-crystal panel configured to modulate or change thepolarization state of the incident light to reflect the light, and toform an image. In this embodiment, the polarization beam splitter 27 maybe further fixed onto the fixed plate 9.

In the first optical path 2, the light from the light source 21 isreflected by the reflector 22 and turned into approximately collimatedlight, passes the first and second fly-eye lenses 23 a, 23 b, isconverted into P-polarized light by the polarization conversion element24, is condensed by the condenser lenses 25 a, 25 b, and reaches themirror 26.

The condensed light reflected by the mirror 26 passes the second opticalpath 5, and enters the polarization beam splitter 27. The polarizationsplitting film 28 transmits the condensed light, such as the P-polarizedlight, and reflects the modulated light, such as the S-polarized light,reflected by the reflective liquid-crystal panel 29 toward theprojection lens 10. The projection lens 10 projects on the projectedsurface 12 light that has passed the third optical path 7 as an image.The projection lens 10 is configured vertically movable by the shifter11.

Second Embodiment

FIG. 4 is an optical path diagram of an image projector according to asecond embodiment corresponding to FIG. 1. In FIG. 4, reference numerals21 to 25 b denote the same elements illustrated in FIG. 3. Referencenumeral 36 denotes a dichroic mirror, Reference 37 denotes apolarization beams splitter (prism) for blue and red. Reference numeral38 denotes a polarization beam splitter (prism) for green. Referencenumeral 39 denotes a color synthesizing prism (synthesizing opticalsystem) configured to reflect a light flux in the green wavelength bandand to transmit light fluxes of red and blue wavelength bands.

Reference numerals 41 and 42 denote polarizing plates. Reference numeral43 denotes a wavelength-selective phase plate configured to rotate apolarization direction of red light by 90°. Reference numeral 45 adenotes a quarter plate for red, and reference numeral 46 a denotes areflective liquid-crystal panel for red. Reference numeral 45 b denotesa quarter plate for blue, and reference numeral 46 b denotes areflective liquid-crystal panel for blue. Reference numeral 45 c denotesa quarter plate for green, and reference numeral 46 c denotes areflective liquid-crystal panel for green. Each color is converted intoP-polarized light or S-polarized light by the wavelength-selective phaseplate 43 and the quarter plates 45 a, 45 b, 45 c.

The dichroic mirror 36 separates white light from the illuminationoptical system (23 a to 25 b) by transmitting first color light, such asgreen light, and by reflecting second color light and third color light,such as red light and blue light. The optical path for the second colorlight and the third color light can be regarded as the second opticalpath 5.

The polarization beam splitter 38 transmits the first color light, suchas P-polarized light, which has transmitted the dichroic mirror 36 andallows that light to reach the reflective liquid-crystal panel 46 c. Thefirst color light, such as S-polarized light, reflected by thereflective liquid-crystal panel 46 c is reflected by the polarizationbeam splitter 38, and reaches the color synthesizing prism 39, and thisoptical path for the reflected light can be regarded as the secondoptical path 5.

The polarization beam splitter 37 reflects the second color light, suchas S-polarized light, reflected by the dichroic mirror 36, and allowsthat light to reach the reflective liquid-crystal panel 46 a. The secondcolor light, such as P-polarized light, reflected by the reflectiveliquid-crystal panel 46 a passes the polarization beam splitter 37, andreaches the color synthesizing prism 39. The polarization beam splitter37 transmits the third color light, such as P-polarized light, reflectedby the dichroic mirror 36, and allows that light to reach the reflectiveliquid-crystal panel 46 b. The third color light, such as S-polarizedlight, reflected by the reflective liquid-crystal panel 46 b isreflected by the polarization beam splitter 37, and reaches the colorsynthesizing prism 39.

The color synthesizing prism 39 synthesizing first color light to thirdcolor light, and introduces the resultant light to projection lens 10.The optical path of the light emitted from the color synthesizing prism39 is the third optical path 7. The projection lens 10 projects thefirst color light to the third colored light that are synthesized withone another, onto the projected surface 12. The projection lens 10 isconfigured movable in the vertical direction by the shifter 11.

This embodiment uses a fixed plate 9A instead of the fixed plate 9. Ofcourse, the fixed plate 9 may be used instead of the fixed plate 9A. Theprojection lens 10 and the shifter 11 are fixed onto the fixed plate 9,whereas the polarization beam splitters (prisms) 37, 38 and the colorsynthesizing prism 39 in addition to them are further fixed onto thefixed plate 9A.

When a positional relationship shifts among the plurality of prisms, theresolution and the image quality lower due to the display pixel shiftsof the reflective liquid-crystal panels 46 a to 46 c and the fall of theoptical components. The fixed plate 9A maintains the positionalrelationship among the plurality of prisms, prevents the optical axis'sshifts, and realizes high image quality. Moreover, since the fixed plate9A is located near the installing surface 3 a of the housing 3, theoptical performance is not deteriorated due to the fixed plate 9A.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-254908, filed Nov. 15, 2010 which is hereby incorporated byreference herein in its entirety.

1. An image projector comprising: an image display element configured todisplay an original image; a first deflector configured to deflect afirst optical path through which light from a light source can pass, andto form a second optical path; a second deflector configured to deflectthe second optical path and to form a third optical path; a projectionlens configured to project light that has transmitted the image displayelement and the third optical path, onto a projected surface; a shifterconfigured to shift the projection lens in a vertical direction whichcorresponds to a longitudinal direction of the projected surface amongdirections orthogonal to an optical axis of the projection lens; ahousing configured to house the image display element, the firstdeflector, and the second deflector; and a fixed plate fixed onto thehousing at an end on an installing surface side of the housing, theprojection lens and the shifter being fixed onto the fixed plate,wherein the third optical path is closer to an installing surface of thehousing than the first optical path.
 2. The image projector according toclaim 1, wherein in the vertical directions, a shift amount by which theshifter can shift the projection lens in a downward directioncorresponding to the installing surface side of the housing is smallerthan a shift amount by which the shifter can shift the projection lensin an upward direction corresponding to a side opposite to theinstalling surface side of the housing.
 3. The image projector accordingto claim 1, wherein a lifting hook is attachable to the installingsurface of the housing, and wherein the image projector furthercomprises an interface substrate mounted with an input/output terminalbetween the first optical path and the installing surface of thehousing.
 4. The image projector according to claim 3, further comprisinga cover member configured to cover the input/output terminal.
 5. Theimage projector according to claim 1, further comprising a prism,wherein the prism is fixed onto the fixed plate.
 6. An image projectorcomprising: an image display element configured to display an originalimage; a first deflector configured to deflect a first optical paththrough which light from a light source can pass, and to form a secondoptical path; a second deflector configured to deflect the secondoptical path and to form a third optical path; a shifter configured toshift a projection lens in a vertical direction among directionsorthogonal to an optical axis of the projection lens; a housingconfigured to house the image display element, the first deflector, andthe second deflector; and wherein the third optical path is closer to aninstalling surface of the housing than the first optical path.
 7. Theimage projector according to claim 6, further comprising a fixed platefixed onto the housing at an end on an installing surface side of thehousing, the projection lens and the shifter being fixed onto the fixedplate,
 8. The image projector according to claim 6, wherein in thevertical directions, a shift amount by which the shifter can shift theprojection lens in a downward direction corresponding to the installingsurface side of the housing is smaller than a shift amount by which theshifter can shift the projection lens in an upward directioncorresponding to a side opposite to the installing surface side of thehousing.
 9. The image projector according to claim 6, wherein a liftinghook is attachable to the installing surface of the housing, and whereinthe image projector further comprises an interface substrate mountedwith an input/output terminal between the first optical path and theinstalling surface of the housing.
 10. The image projector according toclaim 9, further comprising a cover member configured to cover theinput/output terminal.
 11. The image projector according to claim 7,further comprising a prism, wherein the prism is fixed onto the fixedplate.